94 PRACTICAL ORGANIC CHEMISTRY cork of the distilling vessel. It serves to agitate the liquid by introducing a stream of fine air-bubbles which keep it in constant motion. When the water is removed as far as possible, the residue, which forms, on cooling, a thick viscid mass, is mixed with 500 c.c. absolute alcohol. It is heated on the water-bath with reflux condenser for a short time with the addition of a little animal charcoal and filtered. The alcoholic solution is cooled in ice and saturated with dry hydrogen chloride (see p. 93). The liquid is then boiled for FIG. 66. half an hour on the water bath, cooled, and, after dropping in a crystal of the substance, left overnight. Glycocoll ester hydro- chloride crystallises in colourless needles (m. p. 144°) and is filtered and washed with a little alcohol. Yield 10—15 grams. PREPARATION 21. CH<J| Diazoacetic Ester, | \N COOC2H6 Curtius, /. prakt. Chem., 1888, 38, 401 ; Siiberrad, Trans. Chem. Sac., 1902, 81, 600. 25 grams glycocoll ester hydrochrloride (in 50 c.c. of water). 18 ,, sodium nitrite in fine powder.